Just to clear up some stuff for some people, I'm going to explain SOHC and DOHC, since it seems some people don't know the difference. SOHC stands for Single Overhead Cam. This means that the exhaust and intake go through the same valve, which is activated by one cam. DOHC stands for Dual Overhead Cam. This means that there are two cams, each activating one cylinder, which means the exhaust and intake go through two seperate valves.
Please correct me if I'm wrong, but I had to take a AutoBasics course, and might have slept through the whole thing....
